This is the narration that opens Ron Howard’s seafaring epic In The Heart Of The Sea as the camera explores the murky depths, unidentifiable shadows passing through with unnerving enormity. In this modern day, of course, we know that monsters do no exist, but two centuries ago, when whaling vessel the Essex was rammed by a creature of such tremendous size that it cracked its 88-foot newly refitted hull, the word seemed appropriate.

For the crew of the Essex, having their craft destroyed by a large sperm whale during a cursed hunting expedition was just the beginning of one of the most harrowing tales ever told, the kind of story so miraculous it bares retelling. Herman Melville used the events to inspire his classic novel Moby Dick, but the strapping men involved went through perhaps a deeper hell along the way than Ishmael ever did, battling the sea, fear, ego, starvation, and even cannibalism.

“I had no idea that Moby Dick was inspired by a true story,” says Howard who was brought the script, based off of Nathaniel Philbrick’s book, by Australian actor Chris Hemsworth. “I knew that I had to make this movie when I researched it more.”

What we know about the doomed voyage is based off accounts given by the few that survived the ordeal. Different recollections have been shared, but what we do know is that the only reason anyone survived at all is due to a person of incredible bravery named Owen Chase, and the most moving work about the events produced is no doubt his own narrative of the events, titled Shipwreck of the Whale-Ship Essex, which he produced four months after his rescue. Later in his life Chase was declared insane after he was found hoarding food in his attic due to, what would now be recognized as, lingering PTSD from the events.

Chase, played by Hemsworth in the film, was the 23-year-old first mate aboard the Essex serving under Captain George Pollard, played by Ben Walker. At 29, Pollard was particularly young to be commanding a whaling boat, but was descended from a powerful family in the industry. With a crew of 20 souls aboard, the ship left the ports of Nantucket on August 12, 1819 with the purpose of hunting whales and filling up with the animal’s precious natural oil, which at the time was the only fuel source known for lighting lanterns.

The ship was an old one, though recently repaired, and due to a number of successful voyages was deemed by sailors to be a “lucky” ship. That luck ran out pretty quickly when, just two days out, they were hit by a squall that took off the boat’s topgallant, destroyed two whaleboats (smaller crafts used to hunt), and nearly sank her. Instead of turning around for repairs, the Essex pressed on with no intention of returning without its stores full.

The Essex was at sea for over a year before that fateful day that entered it into the history books. Due to overfishing, the vessel was forced to sail farther and farther out, drawing the crew to a newly discovered hunting ground called the “offshore ground,” which was roughly 2,500 nautical miles off the coast of South America. During this journey, Captain Pollard clashed with Chase, a neglectful sailor almost burned the ship to embers, and the crew spoke openly about evil omens that were cursing their voyage. It would seem that their premonitions were right when on November 20, 1820 they spotted a pod of whales and dropped their whaleboats to pursue. Chase harpooned a whale, which began to pull his whaleboat along the water, called a “Nantucket sleighride,” until they were struck by its tail and forced to cut it loose to head back to the Essex for repairs.

Onboard the Essex, Chase was setting to repair his whaleboat when a monstrous animal — crewmembers saying it was around 85 feet (the average size of a sperm whale is 52 feet) — appeared and started to charge the ship, shallow diving to pick up more speed. It crashed into the Essex, sending the crew flying with the boat tipping on its side, and then it floated motionless, seemingly having knocked itself out from the collision. The whale recovered, swimming off a few hundred yards as Chase looked on, turning to face the bow of the ship.

In his own words, Chase recalls that moment in a passage from his book: “I turned around, and saw him about one hundred rods directly ahead of us, coming down apparently with twice his ordinary speed, and to me at that moment, it appeared with tenfold fury and vengeance in his aspect. The surf flew in all directions about him, and his course towards us was marked by a white foam of a rod in width, which he made with the continual violent thrashing of his tail; his head was about half out of water, and in that way he came upon, and again struck the ship.”

Hope was lost for keeping the Essex afloat after the attack, and the crew abandoned ship onto the three remaining whaleboats with what previsions they could salvage. After charting their course, they realized that they would need to travel 4,000 miles without sail to make it back to South America, but that didn’t stop them from pressing on. In just a few weeks they went through their food supplies, and only made their condition by drinking seawater until they miraculously came upon land, now called Henderson Island. There they found food such as eggs and crabs, but were eating through the island’s natural wildlife at an alarming rate. It was Chase who convinced them that they wouldn’t be able to survive on the island indefinitely, suggesting that they continue on the journey.

A few men stayed behind, while the rest set out for Easter Island. No Google Maps or GPS to assist them, they used their knowledge of the sea and charts to determine that a change of course was necessary, adjusting their destination for Más a Tierra Island. It was on this leg of the voyage that the situation became very bleak as they ate through their food stores in days.

The first men who passed away were given the traditional burial at sea, but as hunger grew among the men, throwing away any sustenance, even if the bodies of their comrades, seemed irrational, and they resorted to cannibalism of the dead. Aboard Captain Pollard’s whaleboat, in a circumstance of pure desperation, a decision was made that one of the survivors had to be sacrificed to feed the others, and the group drew lots to see whom it would be. It ended up being Pollard’s young 17-year-old cousin that drew “the black spot.”

In the end, eight men lived, being picked up by passing ships as they drifted into more occupied waters, and they returned to their lives. A few never spoke of the ordeal again, while others chose to share their story, whether it was after months or decades of silence.

During his research for In The Heart of The Sea, which documents some but not all of the story as it happened, Howard says it was these survivor stories that were the most provocative piece of the puzzle: “The accounts of the whale attacking the ship and what happened are so graphic and visceral that we didn’t really have to invent too much.”